Method and system for a low-power client in a wide area network

ABSTRACT

A network device may be operable to receive an indication from a cable modem termination system (CMTS) that media access control (MAC) management messages will be transmitted by the CMTS at fixed intervals. Subsequent to receiving the indication, the network device may be operable to power down one or more components of the network device and set a sleep timer to a value equal to an integer multiple of the fixed interval minus a transition period. The network device may power up the one or more components of the network device upon expiration of the sleep timer. The network device may power up the one or more components of the network device upon an amount of traffic in a buffer of the network device reaching a threshold.

CLAIM OF PRIORITY

This patent application is a continuation of U.S. patent applicationSer. No. 13/866,205 filed on Apr. 19, 2013, which is a divisional ofU.S. patent application Ser. No. 13/553,175 filed in response to arestriction/election requirement. U.S. patent application Ser. No.13/553,175, in turn, makes reference to, claims priority to and claimsbenefit from U.S. Provisional Patent Application Ser. No. 61/547,663filed on Oct. 14, 2011; U.S. Provisional Patent Application Ser. No.61/555,550 filed on Nov. 4, 2011; and U.S. Provisional PatentApplication Ser. No. 61/569,346 filed on Dec. 12, 2011.

Each of the above applications is hereby incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to networking. Morespecifically, certain embodiments of the invention relate to a methodand system for a low-power client in a wide area network.

INCORPORATION BY REFERENCE

This patent application also makes reference to:

-   U.S. patent application Ser. No. 13/485,034 entitled “Method and    System for Server-Side Message Handling in a Low-Power Wide Area    Network,” and filed on May 31, 2012;-   U.S. patent application Ser. No. 13/553,328 entitled “Method and    System for Client-Side Message Handling in a Low-Power Wide Area    Network,” and filed on Jul. 19, 2012; and-   U.S. patent application Ser. No. 13/553,195 entitled “Method and    System for Server-Side Handling of a Low-Power Client in a Wide Area    Network,” and filed on Jul. 19, 2012;

Each of the above applications is hereby incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

Existing wide area networks consume too much power. Further limitationsand disadvantages of conventional and traditional approaches will becomeapparent to one of skill in the art, through comparison of such systemswith some aspects of the present invention as set forth in the remainderof the present application with reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

An system and/or method is provided for a Low-Power Client in a WideArea Network, substantially as illustrated by and/or described inconnection with at least one of the figures, as set forth morecompletely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an exemplary DOCSIS network which may take advantage ofaspects of the invention.

FIG. 2 depicts a cable modem as an example of customer premise equipment(CPE).

FIG. 3 depicts a cable set-top box as an example of customer premiseequipment (CPE).

FIG. 4 depicts a cable gateway as an example of customer premiseequipment (CPE).

FIG. 5A depicts an exemplary physical layer transceiver (PHY) of a CPEwhich supports low-power wide area networking.

FIG. 5B depicts components of a receive chain of an exemplary PHY.

FIG. 5C depicts components of a transmit chain of an exemplary PHY.

FIG. 6 illustrates a media access controller of an exemplary CPE.

FIGS. 7A and 7B illustrate a transition to a state in which MACmanagement messages are transmitted at predetermined intervals.

FIGS. 8A and 8B illustrate activity on a network channel before andduring a CPE entering a power-saving state.

FIG. 9 is a flowchart illustrating exemplary steps for managing apower-saving state in a client device of a wide area network.

FIG. 10 is a flowchart illustrating exemplary steps for managing apower-saving state in a client device of a wide area network.

DETAILED DESCRIPTION OF THE INVENTION

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As utilizedherein, “and/or” means any one or more of the items in the list joinedby “and/or”. As an example, “x and/or y” means any element of thethree-element set {(x), (y), (x, y)}. As another example, “x, y, and/orz” means any element of the seven-element set {(x), (y), (z), (x, y),(x, z), (y, z), (x, y, z)}. As utilized herein, the terms “block” and“module” refer to functions than can be implemented in hardware,software, firmware, or any combination of one or more thereof. Asutilized herein, the term “exemplary” means serving as a non-limitingexample, instance, or illustration. As utilized herein, the term “e.g.,”introduces a list of one or more non-limiting examples, instances, orillustrations.

FIG. 1 depicts an exemplary DOCSIS network which may take advantage ofaspects of the present invention. Shown in FIG. 1 is a terrestrialtelevision antenna 102, a satellite dish 104, an Internet Protocol (IP)network 106, a headend 108, a wide area network (e.g., hybridfiber-coaxial (HFC) network) 118, a gateway 120, end systems 126 a and126 b (e.g., computers), end systems 128 a and 128 b (e.g.,televisions), a cable modem 122 b, and a set-top box 124 b. The headend108 comprises a switch 110, a video modulator 112, a cable modemtermination system (CMTS) 114, and a splitter/combiner 116. The gateway120 may be an instance of the gateway 120 described below with respectto FIG. 4, and may comprise a cable modem module 122 a, and a set-topbox module 124 a. Each of cable modems 122 a and 122 b may be aninstance of the cable modem module 122 described with respect to FIG. 2.Each of set-top boxes 124 a and 124 b may be an instance of the set-topbox module 124 described with respect to FIG. 3.

For downstream traffic, the headend 108 may receive television signalsvia the antenna 102 and the satellite dish 104, and may receive data viathe IP network 106. The switch 110 may convey the television signals tothe video modulator 112 and the data to the CMTS 114. The videomodulator 112 may modulate the received television signals onto acarrier. The CMTS 114 may modulate the received data onto a carrier. Thesplitter/combiner 116 may combine the outputs of the video modulator 112and the CMTS 114 and output the combined signal onto the wide areanetwork (WAN) 118 for distribution to CPE. The cable modems 122 a and122 b may process the portion of the combined signal that carries thedata from the CMTS 114, and the set-top box modules 124 a and 124 b mayprocess the portion of the combined signal that carries the video fromthe video modulator 112.

For upstream data, the end systems 126 a and 126 b may transmit packetsto the cable modem 122 a and 122 b, respectively, which may thenmodulate the packets onto a carrier for transmission via the WAN 118.The splitter/combiner 116 may then convey the data to the CMTS 114. TheCMTS 114 may process the data signals (e.g., verify that they came froma registered cable modem) and convey the data to the IP network 106.

The CMTS 114 may manage connections to the cable modems 122 a and 122 b.This may include, for example: participating in ranging operations tocontrol the power at which the cable modems 122 a and 122 b transmit;forwarding of dynamic host configuration protocol (DHCP) messagesbetween a DHCP server and the cable modems 122 a and 122 b; forwardingof time of day messages between a time of day server and the cablemodems 122 a and 122 b; and managing registration of the cable modems122 a and 122 b to grant the cable modems network (e.g., Internet)access. The registration process for a cable modem 122 may comprise thecable modem 122 sending a registration request along with itsconfiguration settings, and the CMTS 114 accepting or rejecting thecable modem based on the configuration settings. The registrationprocess may additionally comprise an exchange of security keys,certificates, or other authentication information.

Conventionally, after a cable modem has successfully registered with theCMTS 114, the CMTS 114 will deregister the cable modem if the cablemodem does not communicate with the CMTS 114 for a predetermined periodof time. Accordingly, aspects of the present invention may enable acable modem 122 and the CMTS 114 to coordinate the cable modem 122operating in a low-power mode (“sleeping”) without being deregistered bythe CMTS 114. Such coordination between the cable modem 122 and the CMTS114 may be accomplished through communication of one or more messages,as is described, for example, with respect to FIG. 7A and/or FIG. 7B.

Aspects of the invention may enable media access planning in adownstream direction. In this regard, the CMTS 114 may communicate(e.g., via one or more messages) with CPEs (e.g., cable modems) that itserves to coordinate when and how (e.g., on which channel(s)) the CMTS114 will communicate with the CPEs. Downstream planning may enable a CPEto sleep until the next time at which the plan requires it to listen onthe channel(s).

Aspects of the invention may enable the CMTS 114 to dedicate a timeslotfor the transmission of messages to one or more sleeping CPEs. Thetimeslot may occur at intervals that are independently determinable bythe one or more CPEs. That is, duration of the intervals can bedetermined by each of the one or more CPEs without those devices havingto listen for messages outside of the dedicated timeslot. In an exampleembodiment, such an interval may be of a predetermined duration that ismade known to the one or more CPEs prior to the start of the timeslot.In another example embodiment, the duration of such an interval may bedetermined independently by each of the one or more CPEs while theinterval is in progress. In such an embodiment, the determination may bebased on context information (e.g., time of day, previous traffic, etc.)available to the one or more CPEs. Such a scheme may be analogous to anunsolicited grant service, but in the downstream direction. Accordingly,a CPE (e.g., cable modem 122, set-top box 124, or gateway 120) may sleepfor one or more of the intervals between occurrences of the timeslot,wake up and listen to the channel during the timeslot, and then go backto sleep. Such dedicated timeslots in the downstream direction maycoincide in time with, and/or have an independently determinable timerelationship (e.g., a predetermined, fixed time relationship) to,unsolicited grants in the upstream direction. In this manner, if thereis no upstream activity during the corresponding unsolicited grant, thenadjustments may be made to, for example, the duration of the timeslot,the interval between occurrences of the timeslot, etc. The messagescommunicated during occurrences of the timeslot may, for example,contain wake up messages. As another example, the messages communicatedduring occurrences of the timeslot may comprise data communicated toand/or from “always on” end systems (e.g., appliances, utility meters,etc.) that may need to communicate over the WAN via a CPE even when theCPE is in a power-save mode.

In an embodiment of the invention, one or more logical channels may bededicated for the communication of messages (e.g., messages pertainingto power management) and/or for the communication of traffic to“always-on” end systems, even when a CPE via which the “always-on” endsystem communicates is in a power-saving mode. For example, in systemsutilizing DVB-C2 or DVB-T2, such traffic can be mapped to a dedicatedphysical layer pipe.

FIG. 2 depicts a cable modem as an example of customer premise equipment(CPE). The cable modem 122 comprises a physical layer transceiver (PHY)module 202, DOCSIS medium access controller (MAC) module 204, EthernetMAC/PHY module 206, a TCP/IP stack module 208, a conditional accessmodule 210, and a host 218 comprising a CPU 216 and memory module 214which interoperate to execute applications/processes 212.

The PHY module 202 may be operable to receive digital signals from theMAC 204, generate corresponding analog symbols, and transmit the symbolsonto the WAN 118. Similarly, the PHY module 202 may be operable toreceive analog symbols over the WAN 118, convert the symbols to digitalsignals, and convey the digital signals to the MAC module 204. The PHYmodule 202 may be an instance of the PHY module 500 described below withrespect to FIG. 5A. The MAC module 204 may be operable to implementDOCIS media access control protocol(s) for regulating when and/or howthe cable modem 122 transmits on the WAN 118. The Ethernet MAC/PHYmodule 206 may be operable to implement Ethernet physical layer and datalink layer protocols such that the cable modem 220 may transmit andreceive via an Ethernet local area network (LAN). The TCP/IP stackmodule 208 may be operable to implement functionality of OSI layers 3and higher layers to enable the host 218 to communicate via the WAN 118and/or the LAN. The conditional access module 210 may be operable toprevent the host from transmitting and/or receiving DOCSIS traffic viathe WAN 118 if the cable modem 122 is not subscribed to such services.The CPU 216 may execute instructions stored in the memory module 214 andstore run-time data in the memory module 214 to execute variousprocesses and/or applications (e.g., an operating system).

In operation, if and/or when the cable modem 122 operate in apower-saving mode (a mode in which one or more of its componentsnormally used for transmission and/or reception are powered down) may becontrolled based on a variety of factors such as, for example,statistics and/or patterns of traffic in the network, number and/ortypes of devices in the premises served via the modem 122, and/or inputfrom a user in the premises served via the modem 122. Such componentsmay comprise a media access controller (or portions thereof) of thecable modem 122 and/or a PHY (or portions thereof) of the cable modem122. Transitions into and/or out of a power-saving mode may becoordinated via an exchange of messages such as, for example, describedbelow in FIGS. 7A and 7B.

FIG. 3 depicts a cable set-top box as an example of customer premiseequipment (CPE). The set-top box 124 comprises a physical layertransceiver (PHY) module 302, a conditional access module 304, an MPEGdecoder module 306, audio digital-to-analog converter (DAC) module 308,and video encoder module 310.

The PHY module 302 may be operable to receive analog symbols over theWAN 118, convert the symbols to digital signals, and convey the digitalsignals to the MAC module 204. The PHY module 302 may be an instance ofthe PHY module 500 described below with respect to FIG. 5A. Theconditional access module 304 may be operable to prevent the set-top box124 from decoding audio/video content to which it is not subscribed. TheMPEG decoder module 306 may be operable to decode MPEG streams carriedin the signal received via the WAN 118. The Audio DAC module 308 may beoperable to convert one or more digital audio signals output by the MPEGdecoder 306 into an analog signal for output to one or more speakers.The video encoder 310 may be operable to output one or more digitalvideo signals output by the MPEG decoder 306 according to one or morevideo protocols such as HDMI or DisplayPort.

In operation, if and/or when the set-top box 124 operates in apower-saving mode (a mode in which one or more of its componentsnormally used for transmission and/or reception are powered down) may becontrolled based on a variety of factors such as, for example,statistics and/or patterns of traffic in the network, number and/ortypes of devices in the premises served via the set-top box 124, and/orinput from a user in the premises served via the set-top box 124. Suchcomponents may comprise a media access controller (or portions thereof)of the set-top box 124 and/or a PHY (or portions thereof) of the set-topbox 124. Transitions into and/or out of a power-saving mode may becoordinated via an exchange of messages such as, for example, describedbelow in FIGS. 7A and 7B.

FIG. 4 depicts a cable gateway as an example of customer premiseequipment (CPE). The gateway 120 comprises a PHY module 402, a DOCSISMAC module 404, a conditional access module 406, a host controllermodule 408, an Ethernet MAC/PHY module 410, an MPEG decoder module 412,a video encoder module 414, and an audio DAC module 416.

The PHY module 402 may be operable to receive digital signals from theMAC 404, generate corresponding analog symbols, and transmit the symbolsonto the WAN 118. Similarly, the PHY module 402 may be operable toreceive analog symbols over the WAN 118, convert the symbols to digitalsignals, and convey the digital signals to the MAC module 404. The PHYmodule 402 may be an instance of the PHY module 500 described below withrespect to FIG. 5A. The MAC module 404 may be operable to implementDOCIS media access control protocol(s) for regulating when and/or howthe gateway 120 transmits on the WAN 118. The conditional access module406 may be operable to prevent the gateway 120 from decoding audio/videocontent and/or data to which it is not subscribed. The host controllermodule 408 may be operable to implement OSI layer 3 and higher OSIlayers to enable communication between the WAN 118 and the LAN networkvia the Ethernet MAC/PHY module 410. The Ethernet MAC/PHY module 410 maybe operable to implement Ethernet physical layer and data link layerprotocols such that the gateway 120 may transmit and receive via anEthernet local area network (LAN). The MPEG decoder module 412 may beoperable to decode MPEG streams carried in the signal received via theWAN 118. The Audio DAC module 416 may be operable to convert one or moredigital audio signals output by the MPEG decoder 412 into an analogsignal for output to one or more speakers. The video encoder 414 may beoperable to output one or more digital video signals output by the MPEGdecoder 412 according to one or more video protocols such as HDMI orDisplayPort.

In operation, if and/or when the gateway 120 operates in a power-savingmode (a mode in which one or more of its components normally used fortransmission and/or reception are powered down) may be controlled basedon a variety of factors such as, for example, statistics and/or patternsof traffic in the network, number and/or types of devices in thepremises served via the gateway 120, and/or input from a user in thepremises served via the gateway 120. Such components may comprise amedia access controller (or portions thereof) of the gateway 120 and/ora PHY (or portions thereof) of the gateway 120. Transitions into and/orout of a power-saving mode may be coordinated via an exchange ofmessages such as, for example, described below in FIGS. 7A and 7B.

FIG. 5A depicts an exemplary physical layer transceiver (PHY) of a CPEwhich supports low-power wide area networking. The PHY 500 comprises ananalog front end (AFE) 502, a transmit chain 504, a receive chain 506, aclock module 526, and a memory module 528 for storing timing and/orstate information.

For receive operations, the AFE 502 may be operable to amplify an analogsignal received via the WAN 118, down-convert the received signal,filter the received signal, convert the filtered signal to a digitalrepresentation, and convey the digital signal to the demodulator 506.For transmit operations, the AFE 502 may be operable to receive adigital signal from the transmit chain 504, convert the digital signalto an analog representation, filter the analog signal, up-convert thesignal, and amplify the signal for transmission onto the WAN 118. TheAFE 502 may for example, comprise components 552-558 described belowwith respect to FIG. 5B and components 572-578 described below withrespect to FIG. 5C.

The transmit chain 504 may be operable to perform operations to supporttransmission of data onto the WAN 118. Such operations may compriseencoding, modulating, converting to analog, filtering, and/or amplifyinga signal received from higher OSI layers. In an exemplary embodiment ofthe invention, the Tx chain 504 may comprise one or more buffers 510which may be operable to store data to be transmitted while the CPE inwhich the PHY resides is in a power-saving state.

The receive chain 504 may be operable to perform operations to supportreception of data onto the WAN 118. Such operations may compriseamplifying, demodulating, filtering, converting to digital, and/ordecoding a signal received from the physical medium (e.g., coaxialcable). In an exemplary embodiment of the invention, the Rx chain 506may comprise one or more buffers 512 which may be operable to storereceived data while the CPE in which the PHY resides is in apower-saving state.

The clock module 526 may be operable to generate one or more oscillatingsignals for synchronizing circuitry of the PHY 500 and/or for keepingtrack of time. The clock module 526 may, for example, comprise a realtime clock that enables scheduling events such as transitions into andout of a power-saving mode of operation and/or keeping track of when MACmanagement messages, contention opportunities, and/or unsolicitedupstream and/or downstream grants will occur.

The memory module 528 may be operable to store timing information suchas: times at which the CPE is to transition between different modes ofoperation, amount of time the CPE has been in a particular mode ofoperation, times at which a message was received, times at which amessage is expected, etc. Additionally or alternatively, the memorymodule 528 may store state information that may enable the PHY 500 toquickly resume communications upon waking from a power-saving mode. Suchstate info may comprise, for example, upstream frequency to utilize fortransmission, frequency on which to listen for reception, symbol rate atwhich to transmit, modulation profile, carrier offset, equalizer/filtersettings, and/or gain settings. In an exemplary embodiment of theinvention, before components of a CPE (e.g., a MAC of the CPE orportions of the CPE's PHY) go to sleep, those components may store stateinformation to the module 528. This information may be utilized upon thecomponents waking from the power-saving mode to reduce the timenecessary for the components to be ready to receive data from the WAN118.

FIG. 5B depicts components of a receive chain of an exemplary PHY. Thereceive chain 500 comprises the following components: a low noiseamplifier (LNA) module 552, a mixer module 554, a filter module 556, ananalog-to-digital converter (ADC) 558, and a demodulator 560.

The low noise amplifier (LNA) 552 may be operable to amplify signalsreceived via the WAN 118. The mixer 554 may be operable down-convertreceived signals. The filter 556 may be operable to select one or moresub-bands of the received, down-converted signal. The analog-to-digitalconverter (ADC) 558 may be operable to convert the analog signal outputby filter 706 to a digital representation. The demodulator 560 may beoperable to demodulate the digital signal from the ADC 558 to recover anMPEG transport stream (MPEG-TS) contained therein.

In operation, a mode of operation of various components (e.g., amplifier552, mixer 554, filter 556, data converter 558, and demodulator 560) ofthe receive chain 550 may be controlled based on whether the CPE inwhich the receive chain 550 resides is in a power-saving mode. While inthe power-saving mode, one or more of the components may bepowered-down. A component may be powered-down by, for example, reducinga supply voltage and/or supply current provided to the component and/orreducing the frequency of a clock signal input to the component.Additionally or alternatively, components may be powered down byconfiguring them into a different mode of operation. For example, thenumber of poles of the filter 556 may be reduced, the resolution of theADC 558 may be reduced, the gain and/or linearity of the amplifier 552may be reduced, the demodulator 560 may be configured to processlow-order modulation schemes, etc. The configuration of the componentsmay be controlled via the management bus 530.

FIG. 5C depicts components of a transmit chain of an exemplary PHY. Thetransmit chain 570 comprises a power amplifier (PA) module 572, a mixermodule 574, a filter module 576, a digital-to-analog converter (DAC)578, and a modulator 580.

The power amplifier (PA) 572 may be operable to amplify signals fortransmission onto the WAN 118. The mixer 574 may be operable up-convertsignals to be transmitted. The filter 576 may be operable to filter outundesired signals output by the DAC 578. The DAC 578 may be operable toconvert the digital signal output by modulator 580 to an analogrepresentation. The modulator 580 may be operable to modulate a MPEGtransport stream onto one or more carriers.

In operation, a mode of operation of various components (e.g., amplifier572, mixer 574, filter 576, data converter 578, and modulator 580) ofthe transmit chain 570 may be controlled based on whether the CPE inwhich the transmit chain 570 resides is in a power-saving mode. While inthe power-saving mode, one or more of the components may bepowered-down. A component may be powered-down by, for example, reducinga supply voltage and/or supply current provided to the component and/orreducing the frequency of a clock signal input to the component.Additionally or alternatively, components may be powered down byconfiguring them into a different mode of operation. For example, thenumber of poles of the filter 576 may be reduced, the resolution of theADC 578 may be reduced, the gain and/or linearity of the amplifier 572may be reduced, the demodulator 580 may be configured to processlow-order modulation schemes, etc. The configuration of the componentsmay be controlled via the management bus 530.

FIG. 6 illustrates a media access controller of an exemplary CPE. TheMAC 610 may be capable of operating in multiple modes of operation, withdifferent modes of operation being characterized by different powerconsumption. In an exemplary embodiment, the MAC 610 may support a“normal” mode characterized by higher power consumption and a “sleep”mode characterized by lower power consumption, and may occasionallyand/or periodically be put into the sleep mode to reduce powerconsumption.

In some instances, the PHY (e.g., PHY 500) of a CPE may operate in ahigher-power mode (i.e., be “awake”) while the MAC (e.g., MAC 610) ofthe CPE remains in a low-power mode (i.e., be “asleep”). During suchtimes, the PHY may resynchronize a clock utilized for transmittingsignals onto the WAN 118 to the clock utilized for receiving signals viathe WAN 118. Such synchronization may reduce the time needed to be readyto transmit upon the MAC transitioning out of the low-power mode.

In an exemplary embodiment of the invention, channel bonding as enabledin DOCSIS 3.0 may be controlled in coordination with the sleep cycle ofthe CPE. For example, while awake, a CPE may receive and/or transmit onmultiple channels, but while in a sleep mode, only one channel may beallocated for the CPE (the one channel could also be, for example,shared among multiple sleeping CPEs). Communications (e.g., MACmanagement messages and/or other specialized messages or signals)between the CMTS 114 and the CPE in which the AMC 610 resides maycoordinate channel bonding.

FIGS. 7A and 7B illustrate a transition to a state in which MACmanagement messages are transmitted at predetermined intervals.Referring to FIGS. 7A and 7B, there is shown MAP messages n−6 through ncommunicated at non-independently-determinable intervals. That is, fromthe cable modem's perspective the duration of each of the intervals(t3-t1), (t5-t3), (t7-t5), and (t9-t7) are random and, thus the cablemodem has to continuously listen. At time t13, however, the cable modemsends a request that it be permitted to enter a power-saving mode ofoperation. The message may be, for example, a MAC management messagewherein the contents of its Type Value field are uniquely associatedwith a sleep request.

At time t15, the CMTS responds with a message granting the cable modempermission to sleep. The CMTS may determine to grant the request basedon various considerations such as network traffic, type(s) of devices inthe network. The message granting the sleep request may also includeparameters such as how long the cable modem is permitted to sleep,whether the cable modem must listen for messages while it is sleeping,the timing of MAC management messages, contention periods, and/ortimeslots reserved for the cable modem while the modem is sleeping, etc.

Subsequent to the grant at time t15, the CMTS may send MAP messages atindependently determinable intervals until the modem transitions out ofthe power-saving mode back to a normal mode of operation. That is, theduration of each of the intervals (t19-t17), (t21-t19), and (t23-t21) iseither predetermined and known to the cable modem prior to the start ofthe interval, or determinable from context during the interval (withoutthe cable modem having to listen during the interval). In the exampleembodiment depicted, each of the intervals (t19-t17), (t21-t19), and(t23-t21) are of a common, predetermined duration. While in thepower-saving mode, the cable modem may track time such that it knowswhen the next MAP message will be sent. In this manner, should the cablemodem desire, it can transition out of the power-saving state just intime to hear the MAP message, receive and process the MAP message, andthen return to the power-saving state immediately thereafter.

FIGS. 8A and 8B illustrate activity on a network channel before andduring a CPE entering a power-saving state. Shown in these two figuresis activity on an exemplary WAN channel. During timeslots 802, MACmanagement messages, such as UCD, SYNC, and/or MAP messages, may betransmitted by the CMTS. The timeslots 804 may correspond to, forexample, contention periods and/or timeslots reserved for a particularCPE. In FIG. 8A, the timeslots 802 occur atnon-independently-determinable intervals. That is, from the cablemodem's perspective, the duration of each of the intervals Δ1, Δ2, andΔ3 is random and, thus the cable modem has to continuously listen.Similarly, timeslots 804 occur at non-independently-determinableintervals. That is, from the cable modem's perspective, the duration ofeach of the intervals Δ4, Δ5, and Δ6 is random and, thus the cable modemhas to continuously listen. In FIG. 8B, after the CPE has been permittedto enter a power-saving mode of operation, the timeslots 802 and 804occur at predetermined, fixed intervals. That is, the cable modem canindependently determine the duration of each of Δ8-Δ13 and power off andon its receiver accordingly.

FIG. 9 is a flowchart illustrating exemplary steps for managing apower-saving state in a client device of a wide area network. The stepsare described with respect to a cable modem, but may be implemented inother types of devices. The exemplary steps begin with start step 902and proceed to step 904. In step 904, the cable modem connects to theWAN and exchanges messages with the CMTS to be registered on thenetwork. In step 906, the cable modem decides to transition to apower-saving state. This decision may be based, for example, on pasttraffic patterns and/or statistics, expected future traffic, time ofday, type and/or number of devices connected to the cable modem, a levelof service to which the cable modem is subscribed, an amount ofbandwidth that the cable modem has used in the billing period or hasleft to use in the billing period, or any other suitable considerations.

In step 908, the cable modem sends a request for permission totransition to the sleep state. The request may comprise, for example, aMAC management message wherein the contents of its Type Value field areuniquely associated with a request to enter a sleep mode. The messagemay also comprise various information such as, for example, how long thecable modem desires to sleep, the traffic expected by the cable modem,the number and/or types of devices downstream from the cable modem, thechannel(s) on which the cable modem may receive and/or transmit while inthe power-saving mode, the type of signals that the cable modem maytransmit and/or receive while in the power-saving mode, and/or any othersuitable information.

In step 910, it is determined whether the CMTS granted the cable modem'srequest to enter the power-saving mode of operation. If such a grant isnot received, then the exemplary steps advance to step 916 and the cablemodem does not transition to the low-power mode. If, on the other hand,the CMTS does grant the request, then the exemplary steps advance tostep 912.

In step 912, the cable modem may set a sleep timer. The initial and/orterminal value of the timer may be determined based on a variety offactors. For example, the timer may be set based on accuracy (e.g.,drift) of one or more clocks in the cable modem, type and/or number ofdevices downstream of the cable modem (e.g., within the premises servedby the cable modem), past traffic patterns and/or statistics, the timingat which the CMTS has indicated MAC management messages will be sent,the timing at which the CMTS has indicated contention periods will, thetiming at which the CMTS has indicated transmit opportunities for thecable modem will occur, and/or any other suitable factors. The sleeptimer may be set to compensate for an amount of time it takes the cablemodem to transition out of the power-saving state and be ready totransmit or receive. For example, the sleep timer may be set to wake thecable modem up and amount of time, X, before the next MAP message, whereX is the transition time it takes the cable modem to power up circuitryfor receiving a MAP message. As another example, the cable modem maydesire to sleep for two MAP cycles and, therefore, may set its sleeptimer to 2Y-X, where Y is the duration of the interval between MAPmessages.

In step 914, upon expiration of the sleep timer, the cable modem maytransition out of the low-power mode and, in step 916, return to normaloperation.

FIG. 10 is a flowchart illustrating exemplary steps for managing apower-saving state in a client device of a wide area network. The stepsare described with respect to a cable modem, but may be implemented inother types of devices. The exemplary steps begin with start step 1002and proceed to step 1004. In step 1004, the cable modem connects to theWAN and exchanges messages with the CMTS to be registered on thenetwork. In step 1006, the cable modem decides to transition to apower-saving state. This decision may be based, for example, on pasttraffic patterns and/or statistics, expected future traffic, time ofday, type and/or number of devices connected to the cable modem, a levelof service to which the cable modem is subscribed, an amount ofbandwidth that the cable modem has used in the billing period or hasleft to use in the billing period, or any other suitable considerations.

In step 1008, the cable modem sends a request for permission totransition to the sleep state. The request may comprise, for example, aMAC management message wherein the contents of its Type Value field areuniquely associated with a request to enter a sleep mode. The messagemay also comprise various parameters such as, for example, how long thecable modem desires to sleep, the traffic expected by the cable modem,the number and/or types of devices downstream from the cable modem, thechannel(s) on which the cable modem may receive and/or transmit while inthe power-saving mode, the type of signals that the cable modem maytransmit and/or receive while in the power-saving mode, and/or any othersuitable information.

In step 1010, the CMTS decides to permit the cable modem to sleep and,accordingly, transitions to a mode in which it one or more of thefollowing are true: MAC management messages are sent at independentlydeterminable (e.g., predetermined) intervals; contention opportunitiesoccur at independently determinable (e.g., predetermined) intervals;timeslots reserved for communications by the cable modem occur atindependently determinable (e.g., predetermined) intervals.

In step 1012, the CMTS sends the sleep grant to the cable modem. Thesleep grant may comprise, for example, a MAC management message whereinthe contents of its Type Value field are uniquely associated with agrant of permission to enter a sleep mode. The message may also comprisevarious information such as, for example, how long the cable modem ispermitted to sleep, the traffic expected by the CMTS, the channel(s) onwhich the CMTS may receive from and/or transmit to the cable modem whilethe cable modem is in the power-saving mode, the type of signals thatthe cable modem must and/or may transmit and/or receive while in thepower-saving mode, and/or any other suitable information. In step 1014,the cable modem may transition to the power-saving mode.

In step 1016, the cable modem may buffer packets for future processingby the cable modem while it is in the power-saving mode. For example,portions of the PHY may remain powered-up in the low-power mode andthose portions may be operable to receive traffic from the WAN andbuffer it until other portions of the cable modem (e.g., the MAC and/orother portions of the PHY) transition out of the power-saving mode. Asanother example, portions of the MAC may remain powered-up in thelow-power mode and those portions may be operable to receive trafficfrom higher OSI layers (e.g., traffic generated by the host processor ofthe cable modem and/or received from devices in the premises served bythe cable modem) and buffer the traffic until other portions of thecable modem (e.g., the PHY and/or other portions of the MAC) transitionout of the power-saving mode.

In step 1018, upon buffer fullness reaching a set threshold, the cablemodem may wake up and process the buffered traffic. For buffered trafficto be transmitted on the WAN, the transition out of the low-power modemay be timed such that the cable modem is ready to transmit the bufferedtraffic just as the next contention period or timeslot reserved for thecable modem is about to occur. The buffer threshold may be set based on,for example, past traffic patterns and/or statistics, expected futuretraffic, time of day, type and/or number of devices connected to thecable modem, a level of service to which the cable modem is subscribed,an amount of bandwidth that the cable modem has used in the billingperiod or has left to use in the billing period, or any other suitableconsiderations.

Other embodiments of the invention may provide a non-transitory computerreadable medium and/or storage medium, and/or a non-transitory machinereadable medium and/or storage medium, having stored thereon, a machinecode and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the steps as described herein for a low-powerclient in a wide area network.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputing system, or in a distributed fashion where different elementsare spread across several interconnected computing systems. Any kind ofcomputing system or other system adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computing system with a program orother code that, when being loaded and executed, controls the computingsystem such that it carries out the methods described herein. Anothertypical implementation may comprise an application specific integratedcircuit or chip.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

What is claimed is:
 1. A method comprising: in a network device: receiving an indication from a cable modem termination system (CMTS) that contention opportunities will occur at predetermined intervals; subsequent to receiving said indication, transitioning to a power-saving mode in which one or more components of said network device are powered down; transitioning out of said power-saving mode during one of said predetermined intervals, and periodically while operating in said power-saving mode, powering up one or more of said components, resynchronizing to a signal from said cable modem termination system, and again powering down said one or more of said components.
 2. The method of claim 1, wherein said network device is a cable modem, cable set-top-box, or cable gateway.
 3. The method of claim 1, wherein said indication is in response to a request sent by said network device.
 4. The method of claim 1, wherein said one or more components comprise an amplifier, a mixer, a filter, a data converter, a modulator, and/or a demodulator.
 5. The method of claim 1, wherein said one or more components comprise a media access controller.
 6. The method of claim 1, wherein said network device is operable to determine said predetermined time intervals based on past traffic statistics and/or patterns.
 7. The method of claim 1, wherein said network device does not listen to communications from said CMTS while in said power-saving mode.
 8. The method of claim 1, comprising, subsequent to receiving said indication, setting a sleep timer to a value that is determined based on drift of one or more clocks of said network device.
 9. A system comprising: circuitry for use in a network device comprising a buffer, said circuitry being operable to: receive an indication from a cable modem termination system (CMTS) that contention opportunities will occur at predetermined intervals; subsequent to said indication, transitioning to a power-saving mode in which one or more portions of said circuitry are powered down; transition out of said power-saving mode during one of said intervals, and periodically while operating in said power-saving mode, powering up said one or more portions of said circuitry, resynchronizing to a signal from said cable modem termination system, and again powering down said one or more portions of said circuitry.
 10. The system of claim 9, wherein said network device comprises a cable modem, cable set-top-box, or cable gateway.
 11. The system of claim 9, wherein said indication is in response to a request sent by said network device.
 12. The system of claim 9, wherein said one or more portions of said circuitry comprise an amplifier, a mixer, a filter, a data converter, a modulator, and/or a demodulator.
 13. The system of claim 9, wherein said one or more portions of said circuitry comprise a media access controller.
 14. The system of claim 9, wherein said network device is operable to determine said predetermined time intervals based on past traffic statistics and/or patterns.
 15. The system of claim 9, wherein said network device does not listen to communications from said CMTS while in said power-saving mode.
 16. The system of claim 9, wherein said circuitry is operable to, subsequent to reception of said indication, set a sleep timer to a value that is determined based on drift of one or more clocks of said network device. 